In order to stably provide agricultural and horticultural crops, it is essential to control insect pests and diseases. At present, in order to control those diseases and pests, synthetic agrochemicals are widely used due to their excellent economic efficiency and control effect. However, if synthetic agrochemicals are continuously used, their target pests develop resistance to synthetic agrochemicals in some cases. In addition, recently, consumers' consciousness of agrochemicals has been raised, so there is a requirement for an agrochemical which is highly safe to the human body and the environment.
In such a situation, in recent years, pest control compositions having an action mechanism different from synthetic agrochemicals are reported.
Patent Literature 1 discloses a pest control agent containing a water-soluble polymer as an effective component, and discloses that said pest control agent may further contain a surfactant selected from dialkyl sulfosuccinate-based surfactants, silicone-based surfactants, acetylene glycol-based surfactants, polycarboxylic acid-based surfactants and alkylbenzene sulfonic acid salts. This control agent is described as a pest control agent which physically suffocate pests to death so as to control them by spraying onto small pests such as spider mites and aphids injurious to vegetables or fruit trees, directly or after dilution with water 50 to 100 times. In addition, it is described that water-soluble polymer concentration is 100 to 10000 ppm and preferably 500 to 5000 ppm in terms of the effective component concentration, but it is disclosed that in the examples, the control test was carried out on mites using a diluent having a water-soluble polymer concentration of 2000 ppm or 5000 ppm. However, when spraying is carried out at such a high concentration, there is a concern about chemical injury to target crops caused thereby. Further, due to its low dilution factor, preparation of a diluent with water is frequent and cumbersome, and thus worse workability is raised as a problem.
Patent Literature 2 discloses an insecticidal and bactericidal agent for agriculture and horticulture with an effective component being a triglyceride consisting of middle chain fatty acid, which has 8 to 10 carbon atoms, and discloses that it can be mixed with a suitable surfactant or carrier. In addition, Patent Literature 2 describes that the triglyceride consisting of middle chain fatty acid, which have 8 to 10 carbon atoms has a special penetration ability into the skin of small harmful insects such as spider mites, aphids, broad mites, thripses and whiteflies, due to which it is inferred to break the balance of the body fluid, leading to their death, and describes that said insecticidal and bactericidal agent is a composition which physically acts to control.
However, Patent Literature 2 does not describe the effective component concentration in a spray liquid, and in the examples, the above-described insecticidal and bactericidal agent was used at a high concentration to some extent. Specifically, an example is described in which said composition was diluted with water 100 to 500 times and sprayed at an effective component concentration of 1800 ppm, 2250 ppm, 4500 ppm or 9000 ppm. In the case of spraying at such a high concentration, the large amount of the pest control agent to be used and the cumbersome operation of preparing the diluent are raised as problems. In addition, there is a concern about chemical injury to target crops because the middle chain fatty acid triglyceride having a relatively high hydrophobicity is used at a high concentration.
Patent Literature 3 discloses an insecticidal and acaricidal composition containing a certain fatty acid ester and a nonionic surfactant, and describes that said combination has high insecticidal and acaricidal effects compared with other fatty acid esters. More specifically, it discloses an insecticidal and acaricidal composition containing a combination of at least one kind of fatty acid ester selected from the group consisting of glycerol monooleate, glycerol monolinoleate, glycerol monocaprylate, glycerol mono or dioleate, glycerol di or trioleate, glycerol mono or .dilinoleate, glycerol mono or diricinoleate, glycerol diacetomonolaurate, sorbitan laurate, sorbitan oleate, diglycerol laurate, diglycerol oleate, diglycerol monolaurate, diglycerol monooleate, tetraglycerol oleate, hexaglycerol laurate, decaglycerol laurate, propylene glycol monolaurate and propylene glycol monoleate, with a nonionic surfactant. With regard to this composition, it is described that the effective component concentration in a diluent is preferably 0.02 to 10% by weight. It is described that in the examples, said composition was effective on two-spotted spider mites with a water-diluted liquid at a low concentration as an effective component concentration of 70 to 90 mg/100 ml by diluting 1000 times, while it is disclosed that in a test example, said composition was effective on cotton aphids, greenhouse whiteflies and thripses at a concentration of 140 to 180 mg/100 ml as an effective component concentration by diluting 500 times. Accordingly, it is a problem that said insecticidal and acaricidal composition is found to have significant difference in control efficacy between target pest species.